1. Field of the Invention
The present invention generally relates to an ink jet apparatus for forming a given picture image by discharging drops of ink from a discharge port on a recording medium, and more particularly to an ink jet apparatus additionally provided with an improved ink supply mechanism which maintains in good condition the presence of ink within a subsidiary ink tank interposed between a main ink tank and a head.
2. Related Background Art
In a conventional ink jet apparatus, an ink supply system for supplying ink from a main ink tank to a head portion had been so constructed as schematically illustrated in FIG. 6, for example. That is, it is constructed as a system comprising a permanent type head 31 with a subsidiary ink tank, an ink tank 32 for storing ink to be supplied to the head 31 and adapted to be replaceable with respect to the apparatus, a tube 33 connecting the head 31 and the ink tank 32 and used to supply ink therebetween, pump means 34 used for sucking ink from a discharge port 37 of the head 31 and provided with a cap 40 effecting the recovery of ink discharge state, and a tube 35 coupled to part of the subsidiary ink tank of a head different from the discharge port 37 and used for coupling the subsidiary ink tank of the head and the pump means in order to maintain the ink level within the subsidiary ink tank constant by the pump means 34.
Furthermore, as another example, the pump and the subsidiary ink tank are not directly coupled by means of a tube as illustrated in FIG. 7 so as to provide a thin sucking tube 45 above a discharge port 47 to keep the ink level within a subsidiary ink tank 46 of a head 41 constant, contacting a cap 50 against the discharge port 47, and causing ink or air to discharge from the thin tube 45 simultaneously with the recovery of sucking.
However, in the former example, there was required the suction tube 35 in addition to the supply tube 33. Accordingly, two deformable tubes are provided when the ink jet head 31 is mounted on a carriage scanning parallel to the recording medium so that it is difficult to arrange the tubes 33 and 35 within the apparatus, thus leading not only to an increase in production cost, but also to an increase in motor load necessary for the carriage scanning. In addition, fears were entertained that the ink within the suction tubes arranged inside the apparatus may suffer from pressure caused by the scanning of the carriage, and unnecessary variations of pressure against the subsidiary ink tank may occur.
In the examples described above, since the ink jet head 31, 41 and the subsidiary ink tank having various functions of holding ink and air therein, relaxing the pressure variations caused by the carriage scanning, stabilizing the formation of drops of a recording liquid and the discharge thereof, trapping bubbles within the ink tank supply tube, and causing the bubbles not to efflux into the nozzle, are integrally molded into the same member, there is such a drawback that the replacement and repair of the ink jet head by users or repair men at the time of various troubles such as damage to the ink jet heads 31, 41 due to paper jamming, abnormal discharge of ink due to the sticking of foreign matters and the like could not be readily carried out.
In addition, in the later example, since the suction tube 45 used for maintaining the ink level within the subsidiary ink tank constant is made of one thin tube and was constituted in such fashion that it is open externally, there is a fear of effluxing the internal ink toward the outside or taking-in the air from the outside due to the pressure variations within the subsidiary ink tank caused by the carriage scanning at the time of recording, thus leading to a decrease in reliability of the supply of ink.